Active material layer, electrode, and all-solid-state battery

Abstract

This active material layer has an active material, a solid electrolyte, and an electroconductive assistant. The solid electrolyte is expressed by formula (1): LiaEbGcXd. The contact area S1 (m2 / m3) between the active material and the solid electrolyte per unit volume satisfies the expression 365000 < S1 < 385000.

Description

Active material layer, electrode and all-solid-state battery

[0001] This disclosure relates to an active material layer, an electrode, and an all-solid-state battery. This application claims priority based on Japanese Patent Application No. 2024-048859, filed on March 26, 2024, the contents of which are incorporated herein by reference.

[0002] With the remarkable development of electronics technology, portable electronic devices are becoming smaller, lighter, thinner, and more multifunctional. There is also a strong demand for batteries, which serve as the power source for electronic devices, to be smaller, lighter, thinner, more reliable, and safer. All-solid-state batteries, which use solid electrolytes, are attracting attention because they are safer than lithium-ion secondary batteries, which use liquid electrolytes.

[0003] Solid electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, halide-based solid electrolytes, etc. Compared to oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, etc., halide-based solid electrolytes have higher atmospheric stability, higher high voltage resistance, and are more adaptable to various processes.

[0004] The rate characteristic is one of the indicators of rapid charge and discharge, and improvement of the rate characteristic of all-solid-state batteries is desired. For example, Patent Document 1 discloses that the rate characteristic of an all-solid-state battery including a halide-based solid electrolyte is improved by forming a high-halogen region having a high halogen concentration in a solid electrolyte layer.

[0005] Japanese Patent Application Laid-Open No. 2023-127961

[0006] There is a need to study battery configurations that can improve the rate characteristics of all-solid-state batteries, in addition to the configuration disclosed in Patent Document 1.

[0007] The present disclosure has been made in view of the above problems, and aims to provide an all-solid-state battery with excellent rate characteristics. Another aim of the present disclosure is to provide an electrode or active material layer suitable for an all-solid-state battery with excellent rate characteristics.

[0008] In order to solve the above problems, the following means are provided.

[0009] The active material layer according to the first aspect includes an active material, a solid electrolyte, and a conductive additive. ａ E ｂ G ｃ X ｄ In formula (1), E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanoids, and G is OH, BO ２ , B.O. ３ , B.O. ４ , B ３ O ６ , B ４ O ７ , CO ３ , NO ３ , AlO ２ , SiO ３ , SiO ４ , Si ２ O ７ , Si ３ O ９ , Si ４ O １１ , Si ６ O １８ , P.O. ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３ , S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , B.F. ４ , P.F. ６ ,BOB,(COO) ２ , N, AlCl ４ , C.F. ３ SO ３ , C.H. ３ COO, CF ３ COO,OOC-(CH ２ ) ２ -COO,OOC-CH ２-COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH ２ -COO, C ６ H ５ SO ３ , OOC-CH=CH-COO, C(OH)(CH ２ COOH) ２ COO, AsO ４ , Bio ４ , CrO ４ , MnO ４ , PtF ６ , PtCl ６ , PtBr ６ , PtI ６ , SbO ４ , SeO ４ , TeO ４ , HCOO, and O, X is Cl or at least one element selected from the group consisting of Cl and F, Br, and I, a satisfies 0.5≦a<6, b satisfies 0<b<2, c satisfies 0≦c≦6, and d satisfies 0<d≦6.1. In the active material layer according to the first aspect, the contact area S1 (m ２ / m ３ ) satisfies 365000<S1<385000.

[0010] In the active material layer according to the above aspect, the conductive additive may include a first conductive additive and a second conductive additive, wherein the first conductive additive is wire-shaped, and the second conductive additive has a different shape from the first conductive additive.

[0011] In the active material layer according to the above aspect, the second conductive additive may be plate-shaped.

[0012] In the active material layer according to the above aspect, the volume ratio of the first conductive additive may be less than 0.80 times or more than 1.30 times the volume ratio of the second conductive additive.

[0013] An electrode according to a second aspect includes the active material layer according to the above aspect and a current collector connected to the active material layer.

[0014] The electrode according to the above aspect may further include a carbon-containing layer, the carbon-containing layer being located between the active material layer and the current collector.

[0015] An all-solid-state battery according to a third aspect includes the electrode according to the above aspect.

[0016] The all-solid-state battery according to the above embodiment has excellent rate characteristics.

[0017] 1 is a cross-sectional view of an all-solid-state battery according to an embodiment of the present invention;

[0018] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual proportions. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present disclosure is not limited thereto. Appropriate modifications may be made within the scope of the present disclosure.

[0019] "All-Solid-State Battery" FIG. 1 is a cross-sectional schematic diagram of an all-solid-state battery 100 according to this embodiment. The all-solid-state battery 100 shown in FIG. 1 includes a power generating element 40 and an exterior body 50. The exterior body 50 covers the periphery of the power generating element 40. The power generating element 40 is connected to the outside via a pair of terminals 60, 62 connected to the power generating element 40. Although a stacked-type battery is shown in FIG. 1, a wound-type battery may also be used. The all-solid-state battery 100 is used, for example, in laminated batteries, prismatic batteries, cylindrical batteries, coin batteries, button batteries, etc.

[0020] <Power generating element> The power generating element 40 includes a solid electrolyte layer 10, a positive electrode 20, and a negative electrode 30. The power generating element 40 is charged or discharged by the exchange of ions between the positive electrode 20 and the negative electrode 30 via the solid electrolyte layer 10 and the exchange of electrons via an external circuit.

[0021] 1, the negative electrode 30 has a negative electrode current collector 32 and a negative electrode active material layer 34. The negative electrode active material layer 34 is in contact with the negative electrode current collector 32. The negative electrode active material layer 34 is located between the negative electrode current collector 32 and the solid electrolyte layer 10. The negative electrode 30 may be a single layer in which the material constituting the negative electrode current collector 32 and the material constituting the negative electrode active material layer 34 are mixed.

[0022] The negative electrode current collector 32 is conductive. The negative electrode current collector 32 is made of, for example, a metal such as copper, aluminum, nickel, stainless steel, or iron, or a conductive resin. The negative electrode current collector 32 may be in the form of a powder, a foil, a punched piece, or an expanded piece.

[0023] The negative electrode active material layer 34 includes a negative electrode active material, a solid electrolyte, and a conductive additive. The negative electrode active material layer 34 may also include a binder.

[0024] The negative electrode active material may be any compound capable of absorbing and releasing ions, and may be any active material used in known lithium-ion secondary batteries. Examples of the negative electrode active material include carbon materials, metals or alloys capable of reacting with lithium, composite materials of these metals or alloys with carbon materials, oxides, sulfur-modified polyacrylonitrile, metallic lithium, etc. Examples of the carbon material include natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fiber (MCF), cokes, glassy carbon, and organic compound sintered bodies. Examples of the metals or alloys capable of reacting with lithium include Si, SiO ｘ , Sn, aluminum, etc. The oxides include lithium titanate (Li ４ Ti ５ O １２ ), SnO ２ The negative electrode active material is natural graphite or lithium titanate (Li ４ Ti ５ O １２ ) is particularly preferred.

[0025] When the negative electrode active material is a carbon material and the conductive additive is also a carbon material, they can be distinguished by micro-Raman spectroscopy. For example, an area with a side length of 50 μm is measured by micro-Raman spectroscopy, and a Raman mapping classified by the crystallinity of the carbon material is obtained from the Raman spectrum. Because the carbon material functioning as the negative electrode active material and the carbon material functioning as the conductive additive differ in crystallinity, each carbon material is classified as a different region. In the negative electrode active material layer 34, the abundance ratio of the negative electrode active material is higher than the abundance ratio of the conductive additive. Therefore, among the multiple regions classified as carbon materials, the region with a high volume ratio can be determined to be carbon material derived from the negative electrode active material, and the region with a low volume ratio can be determined to be carbon material derived from the conductive additive.

[0026] The median diameter of the negative electrode active material is, for example, 0.7 μm or more and 30 μm or less. When the negative electrode active material and the conductive additive are carbon materials, they can also be roughly distinguished from each other based on the median diameter.

[0027] The volume ratio of the negative electrode active material in the negative electrode active material layer 34 is not particularly limited, but is preferably 30% by volume or more and 80% by volume or less, and more preferably 40% by volume or more and 50% by volume or less. The volume ratio of the negative electrode active material in the negative electrode active material layer 34 can be determined using the density of each material constituting the electrode relative to the true density of the electrode and the ratio thereof. The true density of the electrode can be calculated using the true densities of the materials constituting the electrode and the electrode weight composition ratio. Alternatively, constituent materials may be identified from grayscale differences in a three-dimensional image created from an SEM image, and their proportions in the three-dimensional image may be measured.

[0028] The solid electrolyte is, for example, a halide-based solid electrolyte containing Cl. The solid electrolyte contained in the negative electrode 30 includes a conduction path for lithium ions within the negative electrode.

[0029] The solid electrolyte is Li ａ E ｂ G ｃ X ｄ ... is expressed as (1).

[0030] In formula (1), a represents the composition ratio of Li in the compound represented by formula (1). In formula (1), a satisfies 0.5≦a<6.0. When E is Al, Sc, Y, or a lanthanide, a preferably satisfies 2.0≦a≦4.0, and more preferably satisfies 2.5≦a≦3.5. When E is Zr or Hf, a preferably satisfies 1.0≦a≦3.0, and more preferably satisfies 1.5≦a≦2.5. In the solid electrolyte represented by formula (1), when a satisfies 0.5≦a<6.0, the content of Li contained in the compound becomes appropriate, and the ionic conductivity of the solid electrolyte is increased.

[0031] In formula (1), E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanoids. E is an element that forms the skeleton of the halide-based solid electrolyte represented by formula (1). Lanthanoids are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. A solid electrolyte containing E has a wide potential window and high ionic conductivity. E is more preferably any of Al, Sc, Y, Zr, Hf, and La, and even more preferably Al or Zr.

[0032] In formula (1), b is the composition ratio of E in the compound represented by formula (1). b satisfies 0<b<2.0, and more preferably satisfies 0.6≦b. b may also satisfy b≦1. E is an element having a higher density than the other elements contained in formula (1). An all-solid-state battery containing a solid electrolyte that satisfies b≦1 has a low solid electrolyte density and a large capacity.

[0033] In formula (1), G is substituted with a part of E that forms the framework of the solid electrolyte. The compound of formula (1) may not contain G. G is, for example, OH, BO ２ , B.O. ３ , B.O. ４ , B ３ O ６ , B ４ O ７ , CO ３ , NO ３ , AlO ２ , SiO ３ , SiO４ 、Si ２ O ７ 、Si ３ O ９ 、Si ４ O １１ 、Si ６ O １８ 、PO ３ 、PO ４ 、P ２ O ７ 、P ３ O １０ 、SO ３ 、SO ４ 、SO ５ 、S ２ O ３ 、S ２ O ４ 、S ２ O ５ 、S ２ O ６ 、S ２ O ７ 、S ２ O ８ 、BF ４ 、PF ６ 、BOB、(COO) ２ 、N、AlCl ４ 、CF ３ SO ３ 、CH ３ COO、CF ３ COO、OOC-(CH ２ ) ２ -COO、OOC-CH ２ -COO、OOC-CH(OH)-CH(OH)-COO、OOC-CH(OH)-CH ２ -COO、C ６ H ５ SO ３ 、OOC-CH=CH-COO、C(OH)(CH ２ COOH) ２ COO、AsO ４ 、BiO ４ 、CrO ４ 、MnO ４ 、PtF ６ 、PtCl ６ 、PtBr ６ 、PtI ６ 、SbO ４ 、SeO ４ 、TeO ４, HCOO, and O. G is at least one group selected from the group consisting of PO ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３ , S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , and O. These groups have a strong covalent bond with E. Therefore, when G is contained, E ions are less likely to be reduced, and the solid electrolyte is less likely to be reductively decomposed. A solid electrolyte containing G has a wide potential window on the reduction side and is less likely to be reduced.

[0034] In formula (1), c represents the composition ratio of G in the compound represented by formula (1). c is 0≦c≦6.0, preferably 0.1≦c, and more preferably 0.5≦c. A solid electrolyte containing G in this range has a wide potential window on the reduction side and is less susceptible to reductive decomposition. Furthermore, c is preferably c≦3.0. If the G content is high, the ionic conductivity of the solid electrolyte decreases.

[0035] In formula (1), X is a halide atom. X is an essential atom of the solid electrolyte. X includes Cl. X may consist of Cl alone, or may include Cl together with at least one element selected from the group consisting of F, Br, and I. X has a large ionic radius per valence. By including X, the halide-based solid electrolyte represented by formula (1) allows lithium ions to flow easily and has high ionic conductivity. Furthermore, by including Cl as X, the halide-based solid electrolyte represented by formula (1) has high ionic conductivity and excellent oxidation resistance and reduction resistance.

[0036] In formula (1), d represents the composition ratio of X in the compound represented by formula (1). d satisfies 0<d≦6.1. d preferably satisfies 1.0≦d. When d satisfies 1.0≦d, the strength of the pellet increases when the solid electrolyte is pressure-molded into a pellet. Furthermore, when d satisfies 1.0≦d, the ionic conductivity of the solid electrolyte increases. Furthermore, d preferably satisfies d≦5.0. This is to avoid a situation where an increase in the content of X leads to a shortage of G and a narrowing of the potential window of the solid electrolyte.

[0037] The halide-based solid electrolyte represented by formula (1) is, for example, Li ２ ZrCl ６ , Li ２ ZrSO ４ Cl ４ , Li ２ ZrPO ３ Cl ４ , Li ２ ZrCO ３ Cl ４ , Li ２ Zr((COO) ２ ) ０．５ Cl ５ , Li ２ Zr(CH ３ COO) ０．２ Cl ５．８ , Li ２ Zr(CF ３ COO) ０．２ Cl ５．８ , Li ２ Zr(HCOO) ０．４ Cl ５．６ , Li ２ ZrBO ２ Cl ５ , Li ２ ZrBF ４ Cl ５ , Li ３ YSO ４ Cl ４ , Li ３ YCO ３ Cl ４ , Li ３ YBO ２ Cl ５ , Li ３ YBF ４ Cl ５ , Li２ ZrOCl ４ is.

[0038] The content of the solid electrolyte in the negative electrode active material layer 34 is not particularly limited, but is preferably, for example, 30% by volume or more and 60% by volume or less, and more preferably 40% by volume or more and 50% by volume or less. The volume ratio of the solid electrolyte in the negative electrode active material layer 34 is determined by the same procedure as for the volume ratio of the negative electrode active material.

[0039] In the negative electrode active material layer 34, the contact area S1 between the negative electrode active material and the solid electrolyte per unit volume satisfies 365,000<S1<385,000. The unit of the contact area S1 is m ２ / m ３ The contact area S1 can be calculated using simulation software (GeoDict) developed by Math2Market GmbH. First, the cross section of the sample to be evaluated is observed using an FIB-SEM. The observed image is then three-dimensionalized using the software by connecting images observed in the X-Z plane along the Y-axis. The volume of the three-dimensional structure is calculated from the scale of the SEM image. The electrode material is identified by grayscaling the image during three-dimensionalization. The contact area between the negative electrode active material and the solid electrolyte is measured from the identified electrode material. The contact area S1 per unit area is calculated by dividing this area by the volume of the three-dimensionalized three-dimensional structure. The contact area S1 can be adjusted by designing the amount of conductive additive to be attached to the negative electrode active material in advance at the time of manufacture.

[0040] Examples of the conductive additive include carbon powder, carbon nanotubes, carbon materials, metal fine powder or fiber, a mixture of carbon materials and metal fine powder, and conductive oxides. Examples of the carbon powder include carbon black, acetylene black, and ketjen black. Examples of the metal fine powder include powder or fiber of copper, nickel, stainless steel, iron, etc. The conductive additive improves the electronic conductivity of the negative electrode active material layer 34.

[0041] The volume ratio of the conductive additive in the negative electrode active material layer 34 is preferably, for example, 1.0 volume % or more and 10 volume % or less, and more preferably 2.0 volume % or more and 8.0 volume % or less. The volume ratio of the conductive additive in the negative electrode active material layer 34 is determined by the same procedure as for the volume ratio of the negative electrode active material.

[0042] The conductive additive may include a first conductive additive and a second conductive additive. The first conductive additive is wire-shaped. Wire-shaped means that the wire has a diameter of 50 μm or less and a length at least twice the diameter. The second conductive additive has a different shape from the first conductive additive. The second conductive additive is, for example, plate-shaped. Plate-shaped means that the length along a plane is 1.0 μm or more and 50 μm or less, and the thickness is less than 1.0 μm.

[0043] Carbon nanotubes (CNTs), vapor-grown carbon fibers, and fibers of copper, nickel, stainless steel, iron, etc. are examples of the first conductive additive used in the negative electrode active material layer 34. Graphite, graphene, etc. are examples of the second conductive additive used in the negative electrode active material layer 34.

[0044] The volume ratio of the first conductive additive is preferably 0% to 5.0% by volume, more preferably 1.0% to 4.0% by volume, and even more preferably 1.4% to 3.4% by volume. The volume ratio of the second conductive additive is preferably 1.0% to 10.0% by volume, and more preferably 1.4% to 6.7% by volume.

[0045] The volume ratio of the first conductive additive is preferably less than 0.80 times or more than 1.30 times the volume ratio of the second conductive additive. The relationship between the volume ratio of the first conductive additive and the volume ratio of the second conductive additive can be determined by dividing the volume ratio of the first conductive additive by the volume ratio of the second conductive additive. When the volume ratio of the first conductive additive to the second conductive additive satisfies the above relationship, the rate characteristics of the all-solid-state battery are improved. Although the reason for this is not clear, when the volume ratio of the first conductive additive to the second conductive additive is 1:1, the rate characteristics tend to be lower than when the volume ratio of the first conductive additive is higher than the volume ratio of the second conductive additive, or vice versa.

[0046] The negative electrode active material layer 34 may contain a binder. The binder bonds the negative electrode active material, the solid electrolyte material, and the conductive additive to one another within the negative electrode active material layer 34, and also firmly bonds the negative electrode active material layer 34 to the negative electrode current collector 32. The negative electrode active material layer 34 preferably contains a binder. The binder preferably has reduction resistance and good adhesiveness.

[0047] Examples of binders that can be used in the negative electrode active material layer 34 include polyvinylidene fluoride (PVDF) or copolymers thereof, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polyethersulfone (PES), polyacrylic acid (PA) and copolymers thereof, metal ion crosslinked polyacrylic acid (PA) and copolymers thereof, maleic anhydride-grafted polypropylene (PP), maleic anhydride-grafted polyethylene (PE), and mixtures thereof. Among these, PVDF is particularly preferably used as the binder.

[0048] The binder content in the negative electrode active material layer 34 is not particularly limited, but is preferably 0.00% to 4.0% and more preferably 0.3% to 1.5% by volume based on the total mass of the negative electrode active material, solid electrolyte, conductive additive, and binder. If the binder content is too small, it tends to be difficult to form a negative electrode 30 with sufficient adhesive strength. If the binder content is too high, it tends to be difficult to obtain a sufficient volume or mass energy density because general binders are electrochemically inactive and do not contribute to discharge capacity.

[0049] For example, in the case of powder compaction, the binder does not need to be contained in the negative electrode active material layer 34 .

[0050] 1, the positive electrode 20 has a plate-shaped (foil-shaped) positive electrode current collector 22 and a positive electrode active material layer 24. The positive electrode active material layer 24 is in contact with at least one surface of the positive electrode current collector 22.

[0051] The positive electrode current collector 22 may be made of any conductive material that is resistant to oxidation during charging and corrosion. The positive electrode current collector 22 may be made of, for example, a metal such as aluminum, stainless steel, nickel, or titanium, or a conductive resin. The positive electrode current collector 22 may be in the form of a powder, foil, punched, or expanded.

[0052] The positive electrode active material layer 24 contains a positive electrode active material, a solid electrolyte, a conductive additive, and, if necessary, a binder.

[0053] The positive electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions and insert and extract them (intercalate and deintercalate), and any positive electrode active material used in known all-solid-state batteries can be used. Examples of the positive electrode active material include lithium-containing metal oxides and lithium-containing metal phosphates.

[0054] The lithium-containing metal oxide is, for example, lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), lithium manganese spinel (LiMn ２ O ４ ), and the general formula: LiNi ｘ Co ｙ Mn ｚ O ２ A composite metal oxide represented by (x + y + z = 1), a lithium vanadium compound (LiVOPO ４ , Li ３ V ２ (P.O. ４ ) ３ ), olivine-type LiMPO ４ (wherein M represents at least one selected from Co, Ni, Mn, and Fe), lithium titanate (Li ４ Ti ５ O １２ ) etc.

[0055] The positive electrode active material may not contain lithium. Examples of such a positive electrode active material include lithium-free metal oxides (MnO ２ , V ２ O ５ etc.), lithium-free metal sulfides (MoS ２etc.), lithium-free fluorides (FeF ３ , V.F. ３ When a positive electrode active material that does not contain lithium is used, the negative electrode is doped with lithium ions in advance, or a negative electrode containing lithium ions is used.

[0056] The volume ratio of the positive electrode active material contained in the positive electrode active material layer 24 is the same as the volume ratio of the negative electrode active material contained in the negative electrode active material layer 34 .

[0057] The solid electrolyte contained in the positive electrode active material layer 24 is the same as the solid electrolyte contained in the negative electrode active material layer 34. The volume ratio of the solid electrolyte contained in the positive electrode active material layer 24 is the same as the volume ratio of the solid electrolyte contained in the negative electrode active material layer 34.

[0058] In the positive electrode active material layer 24, the contact area S1 between the positive electrode active material and the solid electrolyte per unit volume satisfies 365,000<S1<385,000.

[0059] The conductive additive contained in the positive electrode active material layer 24 is, for example, the same as the conductive additive contained in the negative electrode active material layer 34. The conductive additive contained in the positive electrode active material layer 24 may have the above-mentioned first conductive additive and second conductive additive. The relationship between the first conductive additive and the second conductive additive contained in the positive electrode active material layer 24 is also the same as the relationship between the first conductive additive and the second conductive additive contained in the negative electrode active material layer 34.

[0060] The positive electrode active material layer 24 may contain a binder. The binder bonds the positive electrode active material, the solid electrolyte material, and the conductive additive to one another within the positive electrode active material layer 24, and also firmly bonds the positive electrode active material layer 24 to the positive electrode current collector 22. The positive electrode active material layer 24 preferably contains a binder. The binder preferably has oxidation resistance and good adhesiveness. The binder contained in the positive electrode active material layer 24 is the same as the binder contained in the negative electrode 30.

[0061] (Solid Electrolyte Layer) The solid electrolyte layer 10 is sandwiched between the positive electrode 20 and the negative electrode 30. The solid electrolyte layer 10 includes a solid electrolyte that can transfer ions by an externally applied voltage. For example, the solid electrolyte conducts lithium ions and inhibits the transfer of electrons.

[0062] The solid electrolyte layer 10 is, for example, a halide-based solid electrolyte. The solid electrolyte layer 10 includes, for example, the above-mentioned solid electrolyte. The solid electrolyte included in the solid electrolyte layer 10 may be different from the above-mentioned solid electrolyte.

[0063] The solid electrolyte layer 10 may contain a binder in addition to the solid electrolyte. The binder may be the same as that used in the positive electrode 20 or the negative electrode 30.

[0064] <Exterior Body> The exterior body 50 houses the power generating element 40 inside. The exterior body 50 prevents moisture and the like from entering from the outside to the inside. As shown in Fig. 1 , the exterior body 50 has a metal foil 52 and a resin layer 54 laminated on each side of the metal foil 52. The exterior body 50 is a metal laminate film in which the metal foil 52 is coated with the resin layer 54 from both sides.

[0065] The metal foil 52 is, for example, aluminum foil or stainless steel foil. The resin layer 54 can be, for example, a resin film such as polypropylene. The materials constituting the inner and outer resin layers 54 may be different. For example, the outer material can be a polymer with a high melting point, such as polyethylene terephthalate (PET) or polyamide (PA), and the inner material can be polyethylene (PE) or polypropylene (PP).

[0066] <Terminals> The terminals 60 and 62 are connected to the negative electrode 30 and the positive electrode 20, respectively. The terminal 62 connected to the positive electrode 20 is a positive electrode terminal, and the terminal 60 connected to the negative electrode 30 is a negative electrode terminal. The terminals 60 and 62 are responsible for electrical connection to the outside. The terminals 60 and 62 are made of a conductive material such as aluminum, nickel, or copper. The connection method may be welding or screw fastening. It is preferable to protect the terminals 60 and 62 with insulating tape to prevent short circuits.

[0067] [Method for Manufacturing All-Solid-State Battery] The positive electrode 20 is manufactured by applying a paste containing a positive electrode active material onto a positive electrode current collector 22 and drying it to form a positive electrode active material layer 24. This paste is produced by carrying out a contact area adjusting step and a pasting step.

[0068] In the contact area adjustment step, the positive electrode active material and the conductive additive are mixed, and a certain amount of the conductive additive is attached to the surface of the positive electrode active material. The amount of the attached conductive additive can be adjusted by adjusting the mass ratio of the positive electrode active material to the conductive additive. The positive electrode active material and the conductive additive may be mixed by mechanochemical treatment. By attaching the conductive additive to the surface of the positive electrode active material in advance, the contact area S1 between the negative electrode active material and the solid electrolyte per unit volume in the positive electrode active material layer 24 can be designed.

[0069] In the pasting step, the positive electrode active material to which the conductive additive is attached and the solid electrolyte are added to a solvent and mixed together. If the mass ratio of the conductive additive attached to the positive electrode active material is smaller than the mass ratio of the conductive additive contained in the positive electrode active material layer 24, additional conductive additive is added to the solvent.

[0070] Next, the negative electrode 30 is prepared. The negative electrode 30 is manufactured by applying a paste containing a negative electrode active material onto a negative electrode current collector 32 and drying it to form a negative electrode active material layer 34. The method for manufacturing the paste containing a negative electrode active material is the same as the method for manufacturing the paste containing a positive electrode active material. In the contact area adjustment step, a conductive additive is applied to the surface of the negative electrode active material in advance, and then the negative electrode active material with the conductive additive applied thereto is made into a paste.

[0071] The power generating element 40 may be fabricated using, for example, a powder molding method. First, as in the contact area adjustment process, a conductive additive is attached to the surface of the positive electrode active material. Next, the positive electrode active material with the conductive additive attached, the solid electrolyte, and the remaining conductive additive are mixed together and then pressure-molded to fabricate the positive electrode 20. A guide with a hole is then placed on the positive electrode 20, and the guide is filled with the solid electrolyte. After that, the surface of the solid electrolyte is smoothed, and the negative electrode 30 is placed on top of the solid electrolyte. The negative electrode 30 is fabricated using a negative electrode active material with the conductive additive attached to its surface. Then, pressure is applied to the positive electrode 20 and the negative electrode 30 to pressure-molde the solid electrolyte. By pressure molding, a laminate is obtained in which the positive electrode 20, the solid electrolyte layer 10, and the negative electrode 30 are stacked in this order.

[0072] Next, external terminals are welded to the positive electrode current collector 22 of the positive electrode 20 and the negative electrode current collector 32 of the negative electrode 30, which form the laminate, by a known method, to electrically connect the positive electrode current collector 22 or the negative electrode current collector 32 to the external terminals. Thereafter, the laminate connected to the external terminals is housed in an exterior body 50, and the opening of the exterior body 50 is hermetically sealed by heat sealing. Through the above steps, the all-solid-state battery 100 of this embodiment is obtained.

[0073] The all-solid-state battery 100 according to this embodiment has excellent rate characteristics. When the conductive additive coats the active material, it prevents contact between the active material and the solid electrolyte. When contact between the active material and the solid electrolyte is prevented, the ion conduction path is reduced, and sufficient output cannot be generated during high-rate charging and discharging. Furthermore, electrons generated in the active material reach the current collector via the conductive additive. If the contact area between the active material and the conductive additive is small, electrons generated during charging and discharging cannot be efficiently transmitted. In the all-solid-state battery according to this embodiment, the contact area S1 between the active material and the solid electrolyte is specified, and both ion conduction paths and electron conduction paths are secured, so sufficient output can be generated even at high rates.

[0074] Furthermore, when the conductive additive contains two types of conductive additives, a first conductive additive and a second conductive additive, the rate characteristics of the all-solid-state battery can be improved. The wire-shaped first conductive additive is responsible for long-distance electron conduction between active materials. The second conductive additive is attached to the surface of the active material and is responsible for short-distance electron conduction. By dividing the roles of the first conductive additive and the second conductive additive, it is possible to increase the number of electron conduction paths while keeping the contact area S1 between the active material and the solid electrolyte within a specified range. With more electron conduction paths, electron paths can be secured even at high rates. As a result, the all-solid-state battery 100 has excellent rate characteristics.

[0075] The above describes the embodiments of the present disclosure in detail with reference to the drawings. However, each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution, and other modifications of the configuration are possible within the scope that does not deviate from the spirit of the present disclosure.

[0076] For example, in the above example, the contact area S1 of both the positive electrode active material layer and the negative electrode active material layer satisfies the predetermined range, but it may be only one of them.

[0077] Furthermore, a carbon-containing layer may be provided between the positive electrode current collector 22 and the positive electrode active material layer 24, or between the negative electrode current collector 32 and the negative electrode active material layer 34. The carbon-containing layer enhances electronic conduction between the positive electrode current collector 22 and the positive electrode active material layer 24, or between the negative electrode current collector 32 and the negative electrode active material layer 34. The carbon-containing layer contains, for example, carbon black, acetylene black, ketjen black, or the like, and a binder. The binder may be the same as that used in the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer.

[0078] Example 1 In Example 1, a charge / discharge half-cell was fabricated and the charge / discharge efficiency was measured. The charge / discharge half-cell of Example 1 was fabricated in the following manner.

[0079] The charge / discharge half-cell was fabricated in a glove box with argon gas circulating at a dew point of approximately -70°C. A lower punch was inserted into a PEEK cylinder of a pellet fabrication jig, and a solid electrolyte Li was placed on top of the lower punch. ２ Zr(SO ４ ) Cl ４ 110 mg of was added.

[0080] The pelletizing jig had a PEEK (polyether ether ketone) cylinder with an outer diameter of 30 mm, an inner diameter of 10 mm, and a height of 20 mm, and upper and lower punches with a diameter of 9.99 mm. The upper and lower punches were made of die steel (SKD11 material).

[0081] The solid electrolyte was prepared by the following procedure. In a glove box filled with an Ar gas atmosphere, lithium sulfate (Li ２ SO ４ ) and zirconium chloride (ZrCl ４) were weighed out so that the molar ratio was 1:1. The raw material powder was placed in a zirconia sealed container for a planetary ball mill, which had already contained zirconia balls. Next, a lid was placed on the sealed container, and the lid was screwed onto the container body. The space between the lid and the container was sealed with polyimide tape. The polyimide tape has the effect of blocking moisture. Next, the zirconia sealed container was set in the planetary ball mill. The raw material powder was subjected to a mechanochemical reaction for 24 hours under conditions of a rotation speed of 500 rpm and a revolution speed of 500 rpm (the rotation direction and the revolution direction were opposite).

[0082] The PEEK cylinder was then vibrated to smooth the surface of the solid electrolyte, after which an upper punch was inserted onto the solid electrolyte and pressed with a press under a load of 373 MPa to form a solid electrolyte layer.

[0083] Next, the upper punch was removed, and 15 mg of a negative electrode mixture was placed on the solid electrolyte layer. The negative electrode mixture contained a negative electrode active material to which a conductive additive had been attached, the above-mentioned solid electrolyte, and a conductive additive. The negative electrode active material was lithium titanate (Li ４ Ti ５ O １２ ) The negative electrode active material with the conductive additive attached was prepared by mixing the negative electrode active material and the conductive additive at a predetermined mass ratio. The mixing was carried out by using a planetary ball mill to mix the negative electrode active material and the conductive additive. The planetary ball mill had a rotation speed of 500 rpm and a revolution speed of 500 rpm. The rotation and revolution directions were opposite to each other. Mixing was carried out for 10 minutes. Next, the solid electrolyte and the remaining conductive additive were added to the negative electrode active material with the conductive additive attached, and mixed for another 5 minutes. Only a plate-shaped carbon material was used as the conductive additive.

[0084] Next, the PEEK cylinder was vibrated to level the surface of the negative electrode mixture. Then, an upper punch was inserted onto the negative electrode mixture and pressed with a press under a load of 373 MPa. Next, the lower punch was removed, and a lithium foil with a diameter of 10 mm and a thickness of 100 μm was placed on the solid electrolyte layer, and the lower punch was inserted. The half cell was configured as a negative electrode active material layer / solid electrolyte layer / Li foil.

[0085] Two stainless steel plates with a diameter of 50 mm and a thickness of 5 mm and two Bakelite® plates with a diameter of 50 mm and a thickness of 2 mm were also prepared. Four screw holes were then formed in each of the two stainless steel plates and the two Bakelite® plates. The screw holes were positioned so that when the half-cell, the two stainless steel plates, and the two Bakelite® plates were stacked, the two stainless steel plates and the two Bakelite® plates would overlap in plan view, but would not overlap with the half-cell in plan view.

[0086] Next, a stainless steel plate, a Bakelite® plate, a half cell, a Bakelite® plate, and a stainless steel plate were stacked in this order, and screws were inserted into the screw holes and tightened with a torque of 1 N m. In this way, a half cell was obtained in which the upper and lower punches of the electrochemical cell were insulated by the Bakelite® plate. Next, the half cell was left to stand in a thermostatic bath at 25°C for 48 hours to stabilize the open circuit voltage.

[0087] The half-cell of Example 1 was charged and discharged under the following conditions to measure the rate characteristics. Charging was performed at a constant current of 0.1 C, and after a constant voltage, charging was terminated when the current reached a value equivalent to 0.05 C. Discharging was performed at 0.1 C (the current value at which charging or discharging is completed in 10 hours when constant current discharging is performed at 25°C), 0.5 C, 1.0 C, and 2.0 C. The discharge capacity when discharging at 0.1 C was defined as 100%, and the ratio of the discharge capacity (rate characteristics (unit: %)) for each of 0.5 C, 1.0 C, and 2.0 C was calculated. Measurements of charge / discharge, charge capacity, and discharge capacity in the charge / discharge test were performed using a charge / discharge device BCS805 (trade name; manufactured by Biologic, Inc.).

[0088] Furthermore, the negative electrode active material layer produced under the same conditions was evaluated using the above-mentioned FIB-SEM and simulation software (GeoDict: Math2Market GmbH), and the respective volume ratios of the negative electrode active material, the solid electrolyte, and the conductive additive, and the contact area S1 between the negative electrode active material and the solid electrolyte per unit volume were determined.

[0089] Examples 2 to 9 and Comparative Examples 1 to 5 Examples 2 to 9 and Comparative Examples 1 to 5 differ from Example 1 in that the volume ratios of the negative electrode active material, the solid electrolyte, and the conductive additive, and the contact area S1 between the negative electrode active material and the solid electrolyte per unit volume were changed.

[0090] The volume ratios of the negative electrode active material, solid electrolyte, and conductive additive were changed by changing the mass ratios of each when preparing the negative electrode composite. The contact area S1 between the negative electrode active material and solid electrolyte per unit volume was changed by changing the mass ratio of the negative electrode active material and the conductive additive when preparing the negative electrode active material to which the conductive additive was attached. In Examples 2 to 7, Example 9, Comparative Example 1, and Comparative Examples 2 to 5, two types of conductive additives were used: a first conductive additive and a second conductive additive. The first conductive additive was a wire-like carbon material, and the second conductive additive was a plate-like carbon material.

[0091] The rate characteristics, the volume ratios of the negative electrode active material, the solid electrolyte, and the conductive additive, and the contact area S1 between the negative electrode active material and the solid electrolyte per unit volume of Examples 2 to 9 and Comparative Examples 1 to 5 were determined in the same manner as in Example 1.

[0092] The results of Examples 1 to 9 and Comparative Examples 1 to 5 are summarized in Table 1. In Table 1, the discharge maintenance ratio corresponds to the rate characteristic.

[0093]

[0094] In Examples 1 to 9, the decrease in discharge capacity was small even at high discharge rates compared to Comparative Examples 1 to 5. This is thought to be because electron conduction paths and ion conduction paths were well formed in the negative electrode active material layer.

[0095] REFERENCE SIGNS LIST 10 solid electrolyte layer 20 positive electrode 22 positive electrode current collector 24 positive electrode active material layer 30 negative electrode 32 negative electrode current collector 34 negative electrode active material layer 40 power generating element 50 exterior body 52 metal foil 54 resin layer 60, 62 terminal

Claims

1. A battery comprising an active material, a solid electrolyte, and a conductive additive, wherein the solid electrolyte is Li ａ E ｂ G ｃ X ｄ ...(1), wherein E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanoids, and G is OH, BO ２ , B.O. ３ , B.O. ４ , B ３ O ６ , B ４ O ７ , CO ３ , NO ３ , AlO ２ , SiO ３ , SiO ４ , Si ２ O ７ , Si ３ O ９ , Si ４ O １１ , Si ６ O １８ , P.O. ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３ , S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , B.F. ４ , P.F. ６ ,BOB,(COO) ２ , N, AlCl ４ , C.F. ３ SO ３ , C.H. ３ COO, CF ３ COO,OOC-(CH ２ ) ２ -COO,OOC-CH ２ -COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH ２ -COO, C ６ H ５ SO ３ , OOC-CH=CH-COO, C(OH)(CH ２ COOH) ２ COO, AsO ４ , Bio ４ , CrO ４ , MnO ４ , PtF ６ , PtCl ６ , PtBr ６ , PtI ６ , SbO ４ , SeO ４ , TeO ４ , HCOO, and O; X is Cl or at least one element selected from the group consisting of Cl and F, Br, and I; a satisfies 0.5≦a<6, b satisfies 0<b<2, c satisfies 0≦c≦6, and d satisfies 0<d≦6.1; and the contact area S1 (m ２ / m ３ ) satisfies 365000<S1<385000.

2. The active material layer according to claim 1, wherein the conductive additive comprises a first conductive additive and a second conductive additive, the first conductive additive is wire-shaped, and the second conductive additive has a shape different from that of the first conductive additive.

3. The active material layer according to claim 2, wherein the second conductive additive is plate-shaped.

4. The active material layer according to claim 2, wherein the volume ratio of the first conductive additive is less than 0.80 times or more than 1.30 times the volume ratio of the second conductive additive.

5. An electrode comprising the active material layer according to claim 1 and a current collector connected to the active material layer.

6. The electrode according to claim 5, further comprising a carbon-containing layer, said carbon-containing layer being between said active material layer and said current collector.

7. An all-solid-state battery comprising the electrode according to claim 5.

Images